Color-converting materials (e.g., phosphor materials) absorb light at certain wavelengths and emit light at different wavelengths. Optical components including color-converting materials are used in a variety of electronic devices, including illumination devices and devices with electronic displays, such as mobile phones, digital cameras, and televisions. In many such devices, color-converting materials are used in conjunction with solid-state radiation transducers (“SSRTs”). Examples of SSRTs include light-emitting diodes, organic light-emitting diodes, and polymer light-emitting diodes. In a common application, a color-converting material is used to modify the light output from an SSRT to include additional or different wavelengths. SSRTs typically emit light having a narrow range of wavelengths. Color-converting materials can absorb some or all of the emitted light and convert it into light having a different range of wavelengths. For example, some SSRT devices include an SSRT that emits blue light and a color-converting material that absorbs some of the blue light and converts it into yellow light. The combination of blue light from the SSRT and yellow light from the color-converting material can appear white. Known color-converting materials useful for this purpose include yttrium aluminum garnet (YAG) doped with various rare earth elements, such as cerium.
Color-converting materials tend to degrade over time to a greater extent than most other materials used in manufacturing electronic devices. For example, certain color-converting materials are prone to react with oxygen or water in the environment. Such reactions can alter the properties of the color-converting materials, which can lower the efficiency of electronic devices including the color-converting materials. Furthermore, color-converting materials often are milled into small particles prior to use, which typically improves their optical properties, but also increases their susceptibility to degradation. A quantity of color-converting material in the form of numerous small particles has a significantly greater surface area available for detrimental reactions than the same quantity of color-converting material in the form of a single structure, such as a block. The choice of particle size in certain applications can be a tradeoff between decreasing particle size to improve optical properties and increasing particle size to slow degradation.
Color-converting materials used in some SSRT devices are particularly prone to degradation. To protect color-converting materials and other sensitive structures, SSRT devices can include a matrix around the color-converting materials, such as an encapsulant matrix. For example, an encapsulant matrix can surround the delicate components of an SSRT device, with the exception of leads or other contacts for electrical connection to a circuit. Common matrix materials include silicone and epoxy. Despite being incorporated into an encapsulant matrix, color-converting materials still degrade, which can adversely affect the reliability and longevity of electrical devices including the color-converting materials. Accordingly, there is a continuing need for innovation related to color-converting materials, such as to improve the reliability and longevity of color-converting materials.